Question: $ E = \left[\begin{array}{rrr}2 & 0 & 1 \\ 1 & 0 & 0 \\ 0 & 2 & 0\end{array}\right]$ What is $ E^{-1}$ ?
Answer: $ = \left[\begin{array}{rrr}0 & 1 & 0 \\ 0 & 0 & \frac{1}{2} \\ 1 & -2 & 0\end{array}\right]$